What are the differences of going with the Kaw spec oil vs SAE 90, 75W90, 85-140, dino or synth?
Disadvantage of the Kaw oil.... It will cost a bunch more than other oil.
Personally, I would stick with a name brand (e.g. Valvoline) synthetic oil. Reasons: You're only going to do it once in a great while, so synthetic is worth the cost. A name brand will be as good as Kaw oil (btw they don't make any oil - a name brand packages it for them)
I've always just bought any SAE 90 oil from my local filling station.
When I buy a used bike changing the oils is one of the things I do, It doesn't cost too much and I count it as part of the cost of the bike.. I don't change the final drive oil every year but about every three years.
John.
I bought a couple of quarts of 85-140 GL5 conventional oil...Valvoline, I think, when I got the bike up and on the road in 2010. I change the final drive oil every other oil change, or every 6000 miles....200 ccs of oil is not much, and a quart will last you a long time. Cheap insurance. I'm still not sold on the "virtue" of synthetic oil....Just in case you don't remember, I have 93,000 miles on the bike, now and the final drive is silent.